The centerpiece of the WRX isn't the standard all-wheel drive that comes with every one (and every Impreza), or the new choices in transmissions. It's the turbocharged, direct-injected 2.0-liter four that swaps in for a less talented, normally aspirated Impreza four.
The turbo four is a tart performer, waking up every joint in the WRX's suspension, using every gear cog (or virtual gear) to magnify the natural handling advantages it has over front-drive compacts with taller powertrain installations. The four's horizontally-opposed cylinders lie flatter, giving it more weight closer to the ground--and all the while, those pistons are turning gas into 268 horsepower and 258 pound-feet of torque, peaking on a wide plateau from 2,000 to 5,200 rpm thanks to different cams and valve springs versus the non-turbo four.
The gearboxes--let's call them that for now--send that sizzling power to all four wheels through a center differential, but there are two mechanically distinct setups. With the six-speed manual gearbox, you get reasonably short shifts and an extra gear versus last year's WRX, along with a viscous-coupling center differential that splits torque 50:50 front to rear. It can distribute torque from the front wheels to the back wheels as traction begins to vary. That setup is pegged by Subaru at a very conservative 5.4 seconds in the 0-60-mph run.
The other transmission technically isn't a gearbox, because there are no gears, just pulleys and simulated gearsteps. It's a continuously variable transmission, one we've sampled in our Best Car To Buy 2014, the Subaru Forester. This CVT probably has better responsiveness than any other CVT we've driven thanks to clever programming: in its "Intelligent" driving mode, it alters its gear ratio constantly to deliver the best fuel economy. In Sport mode, it can be placed in Manual mode, in which it can be paddle-shifted through six pre-set ratios that act and sound like gears.
At its best, the CVT is in Sport Sharp mode, where it responds like a good dual-clutch transmission, with eight virtual gears and swifter throttle response. With the CVT, the WRX gets a different AWD system with a 45:55 rear torque bias and more software connections with the stability control. All told here, the CVT-equipped WRX in its most aggressive mode can reach 60 mph in about 5.9 seconds.
As for STI, it feels sharper and more vivid, but not all that much quicker. It carries forward with the exact same 2.5-liter turbo four as last year, making 305 hp and 290 lb-ft. It's mated to an improved six-speed manual gearbox, and power is delivered via a special Driver Controlled Center Differential (DCCD), bringing a helical limited-slip front differential and Torsen limited-slip rear diff. With it you get bigger Brembo brakes, a stiffer suspension tune (with revised geometry in front), and hydraulic-boost steering with a quicker ratio.
The WRX revels in smooth power transitions, with tightly composed handling and very well-tuned electric power steering. With stiffer shocks, quicker spring rates, bigger-diameter anti-sway bars, and stouter brakes, the WRX has a very taut--almost stiff--feel on a variety of roads that lights up its enthusiast fans and damps enthusiasm for it as a daily driver. It has awesome transient responses, and feels like a critical piece of the design that keeps the ground fastened to the sky--but it can be too rough and tiring in hundred-mile drives with poorly maintained road surfaces. For the fun-driving times, the WRX has electronic torque vectoring--light braking that helps it turn into corners easier, up to a point--and a disable-able traction-control system.
Our major complaint in early WRXs has been with its brakes. The new 17-inch, Dunlop SP Sport Maxx RT tires seem like a willing match to the chassis, but the brakes in two different vehicles we drove felt very numb, and required a very strong foot to tame the drivetrain's eagerness. That's remedied in the WRX STI, which gets high-performance Brembo units in front, and larger stoppers all around.